The present invention relates generally to electromagnetic wave radiators, operating at ultra-high frequencies, and relates more particularly to a wave radiator formed from a plate of a metalized dielectric substrate.
A particularly interesting field of application of the invention is that of small-sized radar antennae operating in a wide frequency band, used either as primary sources illuminating focussing optical systems or as elementary sources for an electronic sweep network antenna for example.
The radio-electric characteristics required at the present time for electronic sweep antenna sweeping space by means of the beam(s) which they radiate are such that it is necessary to use elementary sources taking up little space both in the transverse direction to comply with the pitch between these sources on which the deflection qualities of the antenna depend and in the longitudinal direction so that they are not fragile.
In numerous cases, the solution chosen consists in using either half-wave dipoles printed on a dielectric plate or elements of the "patch" type excited by a microstrip line.
In the example given in the English patent published under the No. 1 348 478, the radiating dipole is fed by a printed slot line on the same face of the dielectric plate as the stems of the dipole, a transition being provided between the slot line and the dipole to ensure good matching.
Since these two types of source only operate correctly as a rule at resonance, they cannot present a large acceptable band-width (standing wave rate less than or equal to 1.5 and radiating diagram without excessive deformation).
For elements of the "patch" type, a band-width of 5% can scarcely by exceeded and for dipoles a double width is considered as good for elements printed on a substrate and excited by a conventional coaxial line.
The aim of the present invention is to remedy these disadvantages by proposing an electromagnetic wave radiator operating over a large frequency band width, having a very compact structure resulting in low radio-electric space occupancy, easy to reproduce and inexpensive, and being able to be used as an element of a linear or two dimensional network antenna with small spacing pitch measured in wave-length.